Charge Equalization Between Series-Connected Battery Cells

ABSTRACT

In one embodiment, a method includes receiving a first input current from a battery through a first connection and a second connection and generating a first output current through a third connection to a first node and a fourth connection to a second node. The first and second nodes are configured to output the first output current to an energy store configured to store a charge. The method includes receiving a second input current through the third connection from the first node and the fourth connection from the second nodes and generating a second output current through the first and second connections to charge the battery.

RELATED APPLICATIONS

This application claims the benefit, under 35 U.S.C. §119(e), of U.S.Provisional Patent Application No. 61/387,294, filed 28 Sep. 2010. Thisapplication also claims the benefit, under 35 U.S.C. §119(a), of GermanPatent Application No. 102010046701.4-32, also filed 28 Sep. 2010.

TECHNICAL FIELD

This disclosure relates to circuits.

BACKGROUND

A battery pack or cell pack (such as for example a Li-Ion cell pack) mayhave multiple battery cells connected in series.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic block circuit diagram of a first exampleembodiment of a circuit for charge equalization.

FIG. 2 shows a schematic circuit diagram of an example embodiment of anenergy-transmission apparatus.

FIG. 3 shows a schematic block circuit diagram of a second exampleembodiment of a circuit for charge equalization.

FIG. 4 shows a schematic block circuit diagram of a third exampleembodiment of a circuit for charge equalization.

DESCRIPTION OF EXAMPLE EMBODIMENTS

This disclosure provides a circuit and a method for charge equalizationbetween series-connected battery cells.

N. H. Kutkut, Dynamic Equalization Techniques for Series Battery Stacks,18TH INTERNATIONAL TELECOMMUNICATIONS ENERGY CONFERENCE, Oct. 6-10,1996, teaches circuits for the dissipative and non-dissipative chargeequalization of series-connected lithium-ion battery cells. Lithium-ionbatteries are operated in frequent instances in rather large seriescircuits of many cells, so-called “stacks” in order to achieve a hightotal voltage. Since the cells are subject to a strong productionleakage it is not possible without additional measures to optimallyfully charge each individual cell. The weakest cell limits the energythat may be removed from the stack or charged into it on account of theseries circuit. It is therefore desirable, in particular given thebackground of the high cost for lithium-ion battery cells, to utilizethe capacity of the stack as optimally as possible. This becomespossible if it is successful by using additional measures to fullycharge each individual cell of the series circuit in accordance with itsmaximal capacity during the charging process and to remove the entireenergy during discharging.

In addition, the capacities of the cells diverge due to aging,self-charging, and other leakage currents over time. This then has theresult that the removable energy in the battery becomes smaller. Therunning time of the apparatus operated with it, e.g., an electric car,therefore becomes shorter. In order to counteract this, the cells mustbe rebalanced again from time to time by a charge equalization.

“Passive balancing” is a method for charge equalization where the cellsthat are just before overcharging are discharged by resistors connectedin parallel to the cell. However, in passive balancing, the entireexcess energy is converted into heat due to energy losses. Recentmethods operate with low-loss storage elements, such as with coils.

Sihua Wen, Cell Balancing Buys Extra Run Time and Battery Life, TEX.INSTRUMENTS INC., ANALOG APPLICATIONS J., 1Q 2009, teaches a circuit forcharge equalization. Energy is pumped from a cell to the adjacent cellthrough the circuit by a coil and two metal-oxide semiconductor (MOS)field effect transistors (FETs) per battery cell. High equalizationcurrents between adjacent cells are possible through the circuit.However, in the normal case the cell that should emit energy and thecell that must receive this energy are not directly adjacent to oneanother but rather separated from one another by a few cells. The chargemust therefore be pumped in several cycles from cell to cell before itfinally arrives where it is actually needed. This drastically reducesthe total degree of effectiveness of the circuit and the equalization ofthe charges takes a long time.

C. Bonfiglio & W. Rössler, A Cost optimized Battery Management Systemwith Active Cell Balancing for Lithium Ion Battery Stacks, VEHICLE POWERAND PROPULSION CONFERENCE, Sep. 7-10, 2009, also teaches a circuit forcharge equalization. A large transmitter is used in the circuit thatcomprises a secondary winding for each battery cell. The single primarywinding may be connected to the entire series circuit of the batterycells. The circuit permits either the energy from the stack to beremoved and to be purposely pushed into any cell or permits the energyto be removed from any cell and to be fed back into the entire stack.The advantage of the circuit is that the cells may be treated in apurposeful manner. Large currents may be generated for the chargeequalization. The required special transmitter is expensive and, inaddition, limits the number of cells that may be equalized by thecircuit.

Particular embodiments provide an improved circuit for chargeequalization.

Particular embodiments provide a circuit for charge equalization betweenseries-connected battery cells. In particular embodiments, the circuitcomprises a first number of first energy-transmission apparatuses. Eachenergy-transmission apparatus may transmit energy for charging anddischarging the associated battery cell. Each first energy-transmissionapparatus is associated with at least one battery cell.

In particular embodiments, each first energy-transmission apparatuscomprises a first connection and a second connection for connecting tothe associated battery circuit. The first and the second connection maybe connected to a housing connection of a semiconductor chip to whichthe associated battery cell may be connected.

In particular embodiments, each first energy-transmission apparatuscomprises a third connection and a forth connection. Each thirdconnection of the first energy-transmission apparatuses is connected toa first node and each forth connection of the first energy-transmissionapparatuses is connected to a second node. In particular embodiments,the currents through the third connections of the energy-transmissionapparatuses are summed up in the first node, and the currents throughthe forth connections are summed up in the second node. The currententers with a positive or negative sign into the summation as a functionof whether the associated battery cell is being charged or discharged.

In particular embodiments, every first energy-transmission apparatus isset up for bidirectional energy transmission. For the bidirectionalenergy transmission each first energy-transmission apparatus is set upto generate a first output current through the third connection and theforth connection using a controlled first input current through thefirst connection and the second connection. In particular embodiments,the first controlled input current discharges the associated batterycell.

In particular embodiments, for the bidirectional transmission of energy,each first energy-transmission apparatus is set up to generate a secondoutput current through the first connection and the second connectionusing a controlled second input current through the third connection andthe forth connection. In particular embodiments, the second outputcurrent charges the associated battery cell.

Particular example embodiments are illustrated in FIG. 1. Theenergy-transmission apparatuses make it possible to transmit energy fromany battery cell to an intermediate storage. As a result of theformation of the energy-transmission apparatuses for the bidirectionaltransmission of energy, charge may be exchanged among the battery cellsalmost as desired. The energy-transmission apparatuses make to possibleto transmit energy in both directions so that each battery cell may becharged or discharged isochronously, yet individually. As a result, theentire stack may be balanced in a very short time. High charging ordischarging currents may be used. It is possible that the chargeequalization may be carried out even during a charging or discharging ofthe entire series circuit, during which each battery cell of the stackmay be fully charged. This increases the range, e.g., of electric cars,or a cheaper battery type may be used. Particular embodiments are aneconomical solution because only relatively few standard structuralelements are used.

Particular embodiments provide an improved method for chargeequalization.

Particular embodiments provide a method for the charge equalizationbetween series-connected battery cells. In particular embodiments, acircuit comprises a number energy-transmission apparatuses. Eachenergy-transmission apparatus is associated with a battery cell. Theenergy-transmission apparatuses are controlled by a control apparatusfor charging or discharging the associated battery cell. In particularembodiments, at least two energy-transmission apparatuses connected vianodes are simultaneously controlled by the control apparatus forcharging or discharging the associated battery cell so that a number ofcurrents of the charging and discharging procedures may be summed up inthe nodes.

In particular embodiments, the first node and the second node may beconnected to an energy store apparatus. In particular embodiments, thefirst node and the second node are connected to different connections ofthe energy store apparatus.

In particular embodiments, the energy store apparatus may be a separatebattery cell. In particular embodiments, the energy store apparatus maybe a capacitor. In particular embodiments, the energy store apparatusmay have a double function as a battery cell of the series-connectedbattery cells.

In particular embodiments, the circuit comprises a second number ofsecond energy-transmission apparatuses. Each second energy-transmissionapparatus is associated with a battery cell of the series circuit ofbattery cells. Each third connection of the second energy-transmissionapparatuses is connected to a third node. Each forth connection of thesecond energy-transmission apparatuses is connected to a fourth node.The currents through the third connections of the secondenergy-transmission apparatuses are summed up here in the third node andthe currents through the fourth connections of the secondenergy-transmission apparatuses are summed up in the fourth node.

In particular embodiments, the first node and the second node areconnected to the third node and to the fourth node by anotherenergy-transmission apparatus for the bidirectional transmission ofenergy. In particular embodiments, the third node and the forth node maybe connected to another energy store apparatus. In particularembodiments, the third node and the fourth node are connected todifferent connections of the energy store apparatus. Thus, energy may beshifted between the energy store and the other energy store by the otherenergy-transmission apparatus.

In particular embodiments, each energy-transmission apparatus has afirst inductor and a second inductor. In particular embodiments, thefirst inductor and the second inductor may be coupled in atransformer-like manner. In particular embodiments, eachenergy-transmission apparatus may comprise a transmitter with the firstinductor that may be designated as the primary winding and with thesecond inductor that may be designated as the secondary winding.

In particular embodiments, each energy-transmission apparatus comprisesat least one first semiconductor switch connected in series to the firstinductor and comprises at least one second semiconductor switchconnected in series to the second inductor. In particular embodiments,the first semiconductor switch and the second semiconductor switch arewired for controlling the transmission of energy. In particularembodiments, the first semiconductor switch and the second semiconductorswitch are transistors, for example, bipolar transistors or FETs.

In particular embodiments, the circuit comprises a control apparatusthat is connected to each energy-transmission apparatus for controllingthe transmission of energy. In particular embodiments, the controlapparatus may be connected to control connections of the firstsemiconductor switch and of the second semiconductor switch of aparticular energy-transmission apparatus. In particular embodiments, thecontrol apparatus may be set up to control an isochronous transmissionof energy from at least two of the energy-transmission apparatuses.

Particular embodiments are advantageous individually as well as incombination. Particular embodiments may be combined with each other. Inorder to simply the discussion, a few possible combinations areexplained in the description of the example embodiments of the figures.However, there are many possible combinations of particular embodiments.

FIG. 1 schematically shows an example circuit for the chargeequalization with an example block circuit diagram. In particularembodiments, the circuit is shown for three battery cells Z₁, Z₂ and Z₃and may be readily expanded to a larger number of battery cells. Inparticular embodiments, for example, the three battery cells Z₁, Z₂ andZ₃ may be readily expanded to sixteen battery cells. Battery cells Z₁,Z₂, Z₃ are connected in series, whereby the cell voltages U_(Z1),U_(Z2), U_(Z3) of cells Z₁, Z₂, Z₃ are added to each other. For theequalization of a different charge of battery cells Z₁, Z₂, Z₃ a firstcell Z₁ with a higher charge is discharged and a second cell Z₂ with alow charge is charged by a discharge of the first cell Z₁. In particularembodiments, during the charging and discharging procedures thedissipation should be as small as possible.

In FIG. 1, two connections of each battery cell Z₁, Z₂, Z₃ are connectedto an energy-transmission apparatus 1-10, 1-20, 1-30. The firstenergy-transmission apparatus 1-10 has a first connection 101 and asecond connection 102 that are connected to the first battery cell Z₁.The second energy-transmission apparatus 1-20 also has a firstconnection 201 and a second connection 202 that are connected to thesecond battery cell Z₂. The third energy-transmission apparatus 1-30 hasa first connection 301 and a second connection 302 that are connected tothe third battery cell Z₃. In particular embodiments, otherenergy-transmission apparatuses and battery cells may be provided in acorresponding manner, as is indicated by dots in FIG. 1.

In particular embodiments, the first energy-transmission apparatus 1-10has a third connection 103 and a forth connection 104. The thirdconnection 103 is connected to a first node 1-81 and the forthconnection is connected to a second node 1-82. In particularembodiments, the first energy-transmission apparatus 1-10 is set up forthe bidirectional transmission of energy between the connections 101,102 on the cell side and between the connections 103, 104 on the nodeside. In particular embodiments, the second energy-transmissionapparatus 1-20 is set up for the bidirectional transmission of energybetween the connections 201, 202 on the cell side and betweenconnections 203, 204 on the node side and the third energy-transmissionapparatus 1-30 is set up for the bidirectional transmission of energybetween connections 301, 302 on the cell side and connections 303, 304on the node side.

In particular embodiments, all third connections 103, 203, 303 ofenergy-transmission apparatuses 1-10, 1-20, 1-30 are connected to thefirst node 1-81. In particular embodiments, all fourth connections 104,204, 304 of the energy-transmission apparatuses 1-10, 1-20, 1-30 areconnected to the second node 1-82. The currents I₁₀₃, I₂₀₃, I₃₀₃ aresummed by the third connections 103, 203, 303 in the first node 1-81. Inparticular embodiments, the currents I₁₀₄, I₂₀₄, I₃₀₄ of the fourthconnections 104, 204, 304 are summed in the second node 1-82. Inaddition, in the exemplary embodiment of FIG. 1 an energy store 1-90 isconnected to the first node 1-81 and to the second node 1-82. Inparticular embodiments, energy store 1-90 may store a charge. Inparticular embodiments, for example, energy store 1-90 is a separatebattery cell or a capacitor. In FIG. 1, the currents I₉₁, I₉₂ of energystore 1-90 additionally enter into the current summation in nodes 1-81,1-82. In particular embodiments, the sum of currents I₁₀₃, I₂₀₃, I₃₀₃,I₉₁ in the first node and the sum of currents I₁₀₄, I₂₀₄, I₃₀₄, I₉₂ inthe second node 1-82 are each zero, so that an energy excess isintermediately stored in energy store 1-90.

Particular embodiments of an example energy-transmission apparatus 1-10are shown in FIG. 2. In particular embodiments, energy-transmissionapparatus 1-10 is set up, based on a controlled first input currentI_(i1) that flows through first connection 101 and second connection102, to generate a first output current I_(o1) that flows through thirdconnection 103 and fourth connection 104.

In particular embodiments, a transmission of energy in the oppositedirection is possible. In particular embodiments, energy-transmissionapparatus 1-10 is set up, based on a controlled second input currentI_(i2) that flows through third connection 103 and fourth connection104, to generate a second output current I_(o2) that flows through firstconnection 101 and second connection 102.

In particular embodiments, energy-transmission apparatus 1-10 may be setup for a separation of potential. In FIG. 2, energy-transmissionapparatus 1-10 comprises a transmitter 110 with a first inductor L₁ andwith a second inductor L₂. In particular embodiments, the first inductorL₁ and the second inductor L₂ may be coupled in a transformer-likemanner M. In particular embodiments, for example, first inductor L₁ andthe second inductor L₂ may be coupled by a material with a high magneticconductivity, such as ferrite. In FIG. 2, a first semiconductor switchM₁ in the form of a first FET M₁ is coupled in series to first inductorL₁. A second semiconductor switch M₂ in the form of a second FET M₂ iscoupled in series to second inductor L₂. In particular embodiments, asan alternative to FETs, other semiconductor switches, such as bipolartransistors, may be used.

In FIG. 2, the first inductor L₁ is connected to the first connection101, the first semiconductor switch M₁ is connected to the secondconnection 102, the second inductor L₂ is connected to the thirdconnection 103 and the second semiconductor switch M₂ is connected tothe fourth connection 104 of energy-transmission apparatus 1-10. Inparticular embodiments, based on the construction size, transmitter 110with inductivities L₁ and L₂ may not be integrated on a semiconductorchip but rather may be connected as an external structural element viathe housing connections 111, 112, 113 114 to the semiconductor chip withsemiconductor switches M₁ and M₂.

In particular embodiments, for control, the control connection (gate) ofthe first semiconductor switch M₁ is connected to a fifth connection 105and the control connection (gate) of the second semiconductor switch M₂is connected to a sixth connection 106 of energy-transmission apparatus1-10. In particular embodiments, for discharging, the transmission ofenergy takes place via energy-transmission apparatus 1-10 in that thefirst semiconductor switch M₁ is controlled by the first control signalen₁ and switches on a first input current I_(i1) via the first inductorL₁. In particular embodiments, a magnetic field is built up by the firstinput current I_(i1). In particular embodiments, the first semiconductorswitch M₁ is subsequently opened and the second semiconductor switch M₂is closed by a control with the second control signal en₂. In particularembodiments, a voltage is induced by the built-up magnetic field in thesecond inductor L₂ which voltage brings about a first output currentI_(o1) via the third connection 103 and the fourth connection 104 whenthe second semiconductor switch M₂ is closed.

In particular embodiments, the transmission of energy for charging cellZ₁ connected to first connection 101 and to second connection 102 takesplace in the opposite direction. In particular embodiments, for chargingcell Z₁, the transmission of energy takes place by energy-transmissionapparatus 1-10 in that the second semiconductor M₂ is controlled by thesecond control signal en₂ and switches on a second input current I_(i2)via second inductor L2. In particular embodiments, a magnetic field isbuilt up by the second input current I_(i2). In particular embodiments,the second semiconductor switch M₂ is subsequently opened and the firstsemiconductor switch M₁ is closed by a control with the first controlsignal en₁. A voltage is induced by the built-up magnetic field in thefirst inductor L₁ which voltage brings about a first output currentI_(o2) via the first connection 101 and the second connection 102 andthus a charging current I_(o2) when the first semiconductor switch M₁ isclosed.

Particular embodiments of an energy-transmission apparatus 1-10, as isshown in FIG. 2, may be readily modified or supplemented. In particularembodiments, for example, it is possible to control a transformationratio between inductivities L₁ and L₂ coupled in a transformer-likemanner M by means of two other semiconductor switches (not shown) and bya coil tap in each instance (not shown). In particular embodiments, itis also possible to switch input current I_(i1) or I_(i2) by controllingthe input-side semiconductor switches as alternating current by means offour semiconductor switches connected to an inductor L₁, L₂ (not shownin FIG. 2), and to rectify (rectifier) the associated output currentI_(o1) and I_(o2) of the other inductor L₁ and L₂ by controlling theoutput-side semiconductor switches (not shown in FIG. 2).

In FIG. 1, a control apparatus 70 is connected to the fifth connections105, 205, 305 and to sixth connections 106, 206, 306 of each of theenergy-transmission apparatuses 1-10, 1-20, 1-30. In particularembodiments, control apparatus 70 may be set up to control anisochronous transmission of energy from at least two of theenergy-transmission apparatuses 1-10, 1-20. In particular embodiments,for example, the first cell Z₁ is discharged and the second cell Z₂charged at the same time. In particular embodiments, for example, adifferent charge of the first cell Z₁ and of the second cell Z₂ isdetermined from particular cell voltage U_(z1), U_(z2) by voltagemeasuring. In particular embodiments, control circuit 70 thenalternately controls the semiconductor switches of the firstenergy-transmission apparatus 1-10 in such a manner that an inputcurrent through connections 101 and 102 generates an output currentthrough connections 103 and 104. In particular embodiments, at the sametime control circuit 70 alternately controls the semiconductor switchesof the second energy-transmission apparatus 1-20 in such a manner thatan input current through connections 203 and 204 generates an outputcurrent through connections 201 and 202. In particular embodiments,output currents I₁₀₃ and I₁₀₄ and input currents I₂₀₃ and I₂₀₄ aresummed up with different signs in nodes 1-81 and 1-82. In particularembodiments, if the currents I₃₀₃ and I₃₀₄ equal zero, then adifferential current flows between output currents I₁₀₃ and I₁₀₄ andinput currents I₂₀₃ and I₂₀₄ as charge/discharge current I₉₁, I₉₂ intoenergy store 1-90.

FIG. 3 schematically shows another example embodiment of a circuit forcharge equalization between series-connected battery cells Z₁₁, Z₁₂,Z_(1n), Z₂₁, Z₂₂, Z_(2n), as a block diagram. In particular embodiments,battery cells Z₁₁, Z₁₂ to Z_(1n) are combined in a first cluster 1. Inparticular embodiments, the first cluster 1 has a first number of firstenergy-transmission apparatuses 1-10, 1-20, 1-n. In particularembodiments, for example, sixteen energy-transmission apparatuses areprovided for sixteen battery cells. Each first energy-transmissionapparatus 1-10, 1-20, 1-n is associated with a battery cell Z₁₁, Z₁₂,Z_(1n).

In particular embodiments, each first energy-transmission apparatus1-10, 1-20, 1-n is connected by two cell-side connections to theassociated battery cell Z₁₁, Z₁₂, Z_(1n). Each first energy-transmissionapparatus 1-10, 1-20, 1-n of the first cluster 1 is connected to a firstnode 1-81 and to a second node 1-82. In particular embodiments, thecurrents of the first energy-transmission apparatuses 1-10, 1-20, 1-nare summed up in the nodes 1-81, 1-82. In particular embodiments, eachfirst energy-transmission apparatus 1-10, 1-20, 1-n is set up for abidirectional transmission of energy. In particular embodiments, acontrol apparatus 70 is connected for controlling the firstenergy-transmission apparatuses 1-10, 1-20, 1-n to eachenergy-transmission apparatus 1-10, 1-20, 1-n.

In particular embodiments, in a second cluster 2 a second number ofsecond energy-transmission apparatuses 2-10, 2-20, 2-n is provided,whereby each second energy-transmission apparatus 2-10, 2-20, 2-n isassociated with one of the series-connected battery cells Z₂₁, Z₂₂,Z_(2n). In particular embodiments, the clustering reduces therequirements on the dielectric strength of the semiconductor elements ofthe circuit so that less chip surface is required.

In particular embodiments, the second energy-transmission apparatuses2-10, 2-20, 2-n are connected to a third node 2-81 and to a fourth node2-82. The currents of the second energy-transmission apparatuses 2-10,2-20, 2-n are summed up in the third and fourth nodes 2-81, 2-82. Inparticular embodiments, every second energy-transmission apparatus 2-10,2-20, 2-n is set up for the bidirectional transmission of energy. Inparticular embodiments, the first and second nodes 1-81 and 1-82 areconnected to the third and fourth nodes 2-81 and 2-82 by anotherenergy-transmission apparatus 1-2 that makes possible a transfer ofenergy between first cluster 1 and second cluster 2. In particularembodiments, control apparatus 70 is connected for the control of thesecond energy-transmission apparatuses 2-10, 2-20, 2-n and of the otherenergy-transmission apparatus 1-2 to them.

In particular embodiments, the first node 1-81 and the second node 1-82are connected to an energy store apparatus 1-90. In FIG. 3, the thirdnode 2-81 and the fourth node 2-82 are connected to another energy storeapparatus 2-90. In particular embodiments, energy store apparatuses1-90, 2-90 may be, for example, separate battery cells.

FIG. 4 schematically shows another example embodiment of a circuit forcharge equalization between series-connected battery cells Z_(M), Z₂₁,Z₂₂ as a block diagram. In particular embodiments, the circuit expensemay be further reduced by using one or more battery cells Z_(M) of theseries circuit as an intermediate store. In FIG. 4, the further batterycell Z_(M) may be connected to the further battery cells Z₂₁, Z₂₂ inseries. The further battery cell Z_(M) is connected to both nodes 2-81and 2-82. In particular embodiments, battery cells Z₂₁, Z₂₂ areconnected by an energy-transmission apparatus 2-10 and 2-20 to nodes2-81 and 2-82. In particular embodiments, the charge equalization ofcells Z₂₁, Z₂₂, Z_(M) occurs via nodes 2-81, 2-82. In particularembodiments, battery cell Z_(M) has dual functionality both as energystore Z_(M) for the intermediate storage during the charge equalizationand as a component of the series circuit for generating a total voltageof the series circuit. The charge equalization of all battery cells Z₂₁,Z₂₂, Z_(M) may occur simultaneously even in particular embodiments. Inparticular embodiments, nodes 2-81, 2-82 are connected (not shown) viatwo further energy-transmission apparatuses 1-2, 2-3 to further nodes offurther clusters. In particular embodiments, even the further nodes maybe connected (not shown in FIG. 4) to a further battery cell of theseries circuit.

Particular embodiments are not limited to the example embodimentsillustrated in FIGS. 1 to 4. Particular embodiments, for example,provide a different energy-transmission apparatus than the apparatusshown in FIG. 2. Particular embodiments may combine a greater or lessernumber of energy-transmission apparatuses for a cluster. Thefunctionality of the circuit according to FIG. 3 may be used for aseries circuit of lithium-ion batteries of a motor vehicle (electriccar).

The following is a list of reference symbols and numbers in FIGS. 1 to4, provided for example illustration purposes only and not by way oflimitation:

-   -   1, 2 cluster    -   1-10, 1-20, 1-30, 1-n, 2-10, 2-20, energy-transmission apparatus    -   2-n, 1-2, 2-3    -   1-81, 1-82, 2-81, 2-82 node    -   1-90, 2-90 energy store, battery cell    -   control apparatus    -   91, 92, 101, 102, 103, 104, 105, connection    -   106, 201, 202, 203, 204, 205, 206,    -   301, 302, 303, 304, 305, 306    -   110 transmitter    -   111, 112, 113, 114 housing connection    -   L₁, L₂ inductor, coil    -   M transformer-like coupling    -   M₁, M₂ semiconductor switch, FET    -   en₁, en₂ control signal    -   I₁₀₃, I₁₀₄, I₂₀₃, I₂₀₄, I₃₀₃, I₃₀₄, I₉₁, I₉₂, current    -   I_(i1), I_(i2), I_(o1), I_(o2), I₁₀₁, I₁₀₁, I₁₀₁, I₁₀₁,    -   I₁₀₁, I₁₀₁, I₁₀₁, I₁₀₁    -   U_(Z1), U_(Z2), U_(Z3), voltage    -   Z_(M), Z₁, Z₂, Z₃, Z₁₁, Z₁₂, Z_(1n), Z₂₁, battery cell, cell    -   Z₂₂, Z_(2n)

Herein, “or” is inclusive and not exclusive, unless expressly indicatedotherwise or indicated otherwise by context. Therefore, herein, “A or B”means “A, B, or both,” unless expressly indicated otherwise or indicatedotherwise by context. Moreover, “and” is both joint and several, unlessexpressly indicated otherwise or indicated otherwise by context.Therefore, herein, “A and B” means “A and B, jointly or severally,”unless expressly indicated otherwise or indicated otherwise by context.

The present disclosure encompasses all changes, substitutions,variations, alterations, and modifications to the example embodimentsherein that a person having ordinary skill in the art would comprehend.Similarly, where appropriate, the appended claims encompass all changes,substitutions, variations, alterations, and modifications to the exampleembodiments herein that a person having ordinary skill in the art wouldcomprehend. Moreover, reference in the appended claims to an apparatusor system or a component of an apparatus or system being adapted to,arranged to, capable of, configured to, enabled to, operable to, oroperative to perform a particular function encompasses that apparatus,system, component, whether or not it or that particular function isactivated, turned on, or unlocked, as long as that apparatus, system, orcomponent is so adapted, arranged, capable, configured, enabled,operable, or operative.

1. A circuit comprising: a first node coupled to an energy transmitter;a second node coupled to the energy transmitter; and the energytransmitter, configured to: receive a first input current from a batterythrough a first connection and a second connection; generate a firstoutput current through a third connection to the first node and a fourthconnection to second node; receive a second input current through thethird and fourth connections from the first and second nodes; andgenerate a second output current through the first and secondconnections to charge the battery.
 2. The circuit of claim 1, whereinthe energy transmitter comprises: a transmitter comprising a firstinductor coupled to a second inductor; a first semiconductor switchcoupled in series to the first inductor and coupled to the secondconnection; and a second semiconductor switch coupled in series to thesecond inductor and coupled to the fourth connection.
 3. The circuit ofclaim 2, wherein the first and second inductors are coupled in atransformer-like manner.
 4. The circuit of claim 1, further comprising acontroller coupled to a fifth and sixth connection of the energytransmitter and configured to control the transmission of energy.
 5. Thecircuit of claim 4, wherein: the battery is coupled in series to one ormore other batteries, each of other batteries being coupled to one ormore other energy transmitters, the other energy transmitters beingcoupled to the controller; and the controller is configured to controlan isochronous transmission of energy from the energy transmitter and atleast one of the other energy transmitters.
 6. The circuit of claim 1,further comprising an energy store coupled to the first and secondnodes, the energy store being configured to store a charge.
 7. Thecircuit of claim 6, wherein the energy store comprises one of anotherbattery or a capacitor.
 8. A method comprising: receiving a first inputcurrent from a battery through a first connection and a secondconnection; generating a first output current through a third connectionto a first node and a fourth connection to a second node, the first andsecond nodes configured to output the first output current to an energystore configured to store a charge; receiving a second input currentthrough the third connection from the first node and the fourthconnection from the second nodes and generating a second output currentthrough the first and second connections to charge the battery.
 9. Themethod of claim 8, wherein the energy store comprises one of anotherbattery cell or a capacitor.
 10. A system comprising: a battery; anenergy transmitter coupled to the battery via a first connection and asecond connection; a first node coupled to a third connection of theenergy transmitter; a second node coupled to a fourth connection of theenergy transmitter; and the energy transmitter, configured to: receive afirst input current from the battery through the first and secondconnections; generate a first output current through the third andfourth connections to the first and second nodes; receive a second inputcurrent through the third and fourth connections from the first andsecond nodes; and generate a second output current through the first andsecond connections to charge the battery; a controller coupled to afifth and sixth connection of the energy transmitter and configured tocontrol the transmission of energy; and an energy store coupled to thefirst and second nodes, the energy store being configured to store acharge.
 11. The system of claim 10, wherein the battery is coupled inseries to one or more other batteries, each of other batteries beingcoupled to one or more other energy transmitters, the other energytransmitters being coupled to the controller; and the controller isconfigured to control an isochronous transmission of energy from theenergy transmitter and at least one of the other energy transmitters.12. The system of claim 10, wherein the energy transmitter comprises: atransmitter comprising a first inductor coupled to a second inductor; afirst semiconductor switch coupled in series to the first inductor andcoupled to the second connection; and a second semiconductor switchcoupled in series to the second inductor and coupled to the fourthconnection.
 13. The system of claim 12, wherein the first and secondinductors are coupled in a transformer-like manner.
 14. The system ofclaim 10, wherein the energy store comprises one of another battery or acapacitor.